A system stabilizing controller precalculates generator shedding information for assumed fault cases at constant intervals using online data of grid information and, when a fault occurs in the grid, performs generator shedding of an appropriate generator using precalculated information before a group of generators in the grid oscillates or steps out under the influence of the fault. On the other hand, even when a precalculation cannot be performed due to a fault of the system stabilizing controller or the like, generator shedding information suitable for a present grid state must be calculated so that a shortage in a generator shedding amount does not occur.
As conventional art, PTL 1 reports a method of estimating generator shedding information suitable for a present grid state using history data of previously calculated generator shedding information. Specifically, every time generator shedding information is precalculated at constant intervals by a system stabilizing controller, a data pair constituted by a power flow amount and a generator shedding amount at each fault observation point is accumulated as two-dimensional generator shedding amount data. A correlation line representing a relationship between the power flow amount and the generator shedding amount at each fault observation point is estimated in advance from history data of the generator shedding amount and, when a grid fault is detected, a necessary generator shedding amount is instantaneously determined from a relationship between a present cross-sectional power flow and the correlation line and generator shedding is performed by a combination with a generator with a smallest generator shedding amount exceeding the necessary generator shedding amount.